Increment patterns in otoliths and scales from mature Atlantic salmon Salmo salar

Abstract

This is the first work to note a similarity in increment patterns between otoliths and scales up to maturation, helping to understand better the biological and physical mechanisms guiding otolith and scale growth and increment formation. We demonstrate, with returning 1- and 2-sea winter Atlantic salmon Salmo salar, that transverse otolith thin sections to the core expose increments that represent seasonal growth during the marine phase. These increments are similar to those that form on scales, albeit with greater increment-width variability. From cage-reared fish, we noted that the number of increments on otoliths and scales formed during the period of marine residence is the same, and that the average mean deposition-time is slightly over 1 wk in the first year and ca. 2 wk in the second year.